在网上得到一个能够实现在菜单栏中查看历史信息的代码，自己修改了一下，在运行时遇到错误  错误    1    当前上下文中不存在名称“menuitem_Click”    E:\C#Practice\Ex01_01\Ex01_01\Form1.cs    53    52    Ex01_01

using System;
using System.Collections.Generic;
using using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

using namespace Ex01_01
{
    public partial class Form1 : Form
    {
        public string address = @"E:\C#Practice\Ex01_01";

        public Form1()
        {
            InitializeComponent();
        }
        //自定义方法ShowWindows()用来家在背景图片应显示窗体
        public void ShowWindows(string fileName)
        {
            Image p = Image.FromFile(fileName);
            Form f = new Form();
            f.MdiParent = this;
            f.BackgroundImage = p;
            f.Show();
        }

        //将打开文件路径写入INI文件中
        private void 打开ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            openFileDialog1.FileName = "";
            this.openFileDialog1.ShowDialog();
            StreamWriter s=new StreamWriter(address + "\\menu.ini",true);
            s.WriteLine(openFileDialog1.FileName);
            s.Flush();
            s.Close();
            ShowWindows(openFileDialog1.FileName);
        }

        //读取INI文件并将信息加入菜单
        private void Form1_Load(object sender, EventArgs e)
        {
            StreamReader sr=new StreamReader(address+"\\Menu.ini");
            int i=this.文件ToolStripMenuItem.DropDownItems.Count-2;
            while(sr.Peek()>=0)
            {
                ToolStripMenuItem menuitem=new ToolStripMenuItem(sr.ReadLine());
                this.文件ToolStripMenuItem.DropDownItems.Insert(i,menuitem);
                i++;
                menuitem.Click += new EventHandler(menuitem_Click);
            }
            sr.Close();
        }
    }
}

menuitem.Click += new EventHandler(menuitem_Click);
这句代码的作用我不理解  所以不知道怎么改